We have examined the status of the cytochromebc1 complex in mitochon-drial membranes from yeast mutants in which genes for one or more of the cytochromebc1 complex subunits were deleted. When membranes from wild-type yeast were resolved by native gel electrophoresis and analyzed by immunodecoration, the cytochrome bc1 complex was detected as a mixed population of enzymes, consisting of cytochromebc1 dimers, and ternary complexes of cytochromebc1 dimers associated with one and two copies of the cytochrome c oxidase complex
